1. Field of the Invention
The present invention relates to a reactor to cause reaction of a reactant, particularly to a reactor comprising a vacuum heat insulating structure.
2. Description of Related Art
In recent years, a research and development for putting a fuel cell into practice has been greatly promoted as a clean power supply with high energy conversion efficiency for equipping the fuel cell with vehicles, portable equipment and the like. The fuel cell is equipment to allow a fuel to electrochemically react with oxygen in the air for directly extracting electric energy from chemical energy. Also, a research and development for downsizing a power source system using the fuel cell has been promoted to enable the power source system to be applied to a cell phone, electric vehicle and the like as a power source unit.
As a fuel used for the fuel cell, simple hydrogen can be given. There is a problem in handling hydrogen because simple hydrogen is a gas at ordinary temperature and pressure. Although there has been an attempt to store hydrogen with a hydrogen absorbing alloy, the storage amount of hydrogen per unit volume has been small and insufficient especially as a fuel storage unit for a power supply of compact electronic equipment such as portable electronic equipment.
On the other hand, a reformer fuel cell which reforms a liquid fuel having hydrogen atoms in the composition thereof such as alcohols and gasoline and utilizes the generated hydrogen can easily keep a fuel in a liquid state. Such a power source system comprising a reformer fuel cell may require a reactor comprising a reaction container such as a vaporizer for vaporizing a liquid fuel and water, a reformer for extracting hydrogen necessary for power generation by reacting a vaporized liquid fuel with a high-temperature water vapor, a carbon monoxide remover for removing carbon monoxide which is a by-product of the reforming reaction, and the like.
To downsize such a reactor, microreactors have been developed in which a vaporizer, reformer, and carbon monoxide remover are stacked up, and a groove is formed by joining a metal substrate so as to work as a reaction channel to cause the above-described various reactions.
An operating temperature of a vaporizer and carbon monoxide remover has less than 200° C., and that of a reformer is 250° C. or more. In order to keep the temperature, to ensure safety by preventing heat in a reformer and carbon monoxide remover leaking outside and to improve heat efficiency by reducing loss of heat energy, a container to make vacuum condition around a reformer and monoxide remover may be installed to be a vacuum heat insulating structure.
To form such a vacuum heat insulating structure, an insulating container to cover the reformer and carbon monoxide remover is provided and the inner space of the insulating container becomes vacuum condition. However, such vacuum insulation structure has a problem such that a leak is caused on the insulating container through a gap or the like formed in the production and air breaks in from outside, and that residual gas molecule absorbed on a surface of each reaction container or inner surface of the insulating container is released. In such case, vacuum around a reformer and carbon monoxide remover is down to decrease insulation property, so that heat leaks outside and heat loss increases. It is known to provide a getter material to inside of the insulating container to improve degree of vacuum of the inner space. However, because a certain volume is required to install a getter material, there is a problem that the getter material obstructs downsizing of the reactor.